Since the advent of steering column air bag assemblies, engineers have struggled with designs for a horn switch. Air bag cover doors, located in the center of the steering column where horn switches had been located, require that old horn switches be moved or modified to accomodate the air bag assembly. This is because the cover doors cover and retain the air bag assembly in place and because the cover door must rupture in a predetermined fashion. Initially, designers were reluctant to place switches on the cover door itself, fearing that the switch may interfere with the rupturing of the cover door when the air bag activated, or worse, that the switch may fly off the door and injure the occupants of the vehicle. Some designers placed the horn switch behind the cover door, but this made repair and replacement of the switch difficult and expensive. Other designers placed one or more horn switches on the sides of the cover door; but drivers in emergency situations have difficulty finding the switch, and instead jam their palms onto the insensitive and mute cover door in a futile attempt to berate the mischievous pedestrian or motorist they happen to encounter.
U.S. Pat. No. 5,002,306 to Hiramitsu et al. teaches an air bag cover door with a horn switch mounted thereon. The horn switch is safely spaced away from the tear seam of the cover door, and thus will not interfere with its rupturing; but the switch is molded into the surface of the cover door and cannot be replaced easily.
U.S. Pat. No. 5,186,490 to Adams et al. also teaches an air bag cover door with a horn switch disposed thereon. The horn switch is replaceable; but the switch cover for the switch extends over the cover door tear seam, and seems likely to interfere with the rupturing of the cover door. Moreover, the switch cover is unnecessarily complicated, being in two pieces where one of the pieces is permanently molded onto the cover door.